Neither man would appreciate the comparison, but there is one striking similarity between George Bush and Hugo Chavez. Both are radical Presidents who see the world as a struggle between good and evil, with no middle way.

Venezuela will decide today if it is with Chavez and his ambition to reinvent the country through a referendum on constitutional reform. If a majority votes in favour, South America's oil giant will enshrine socialism and abolish term limits, enabling the President to keep running for office for decades.

If a majority votes no, as some opinion polls suggest, it will put a brake on the 'Bolivarian revolution' and deliver Chavez's first serious political defeat in nine years.

Initially the President campaigned on the proposed changes, assuming that a document which cut the working day from eight to six hours, beefed up communal councils, and extended pensions and benefits to housewives and street vendors would be popular.

But those sweeteners received less attention than vaguely worded provisions about amending property rights and extending presidential power, prompting anxiety about Cubanisation.

It was not just the middle class and the Catholic church but many within the ranks of Chavez's movement who objected. High-profile defections to the opposition, against a backdrop of food shortages and high inflation, seemed to tilt a majority against the referendum.

At which point Chavez, a former tank commander, followed the playbook of Bush, whom he has called a donkey, an alcoholic and a genocidal war criminal. Like the 'war on terror', the constitutional reform was deemed an existential issue.

Oppose it, said Chavez, and you are a 'traitor'. Socialist allies who baulked at certain provisions were branded CIA stooges and expelled from the movement. Loyalists who suggested that was harsh were also expelled. 'It's black and white,' said the President. 'A vote against the reform is a vote against Chavez.'

Turning the referendum into a plebiscite on his rule is smart. Chavez remains extremely popular with the poor for spending oil revenues on schools and clinics in the barrios. Many who were dubious about the constitutional changes had considered voting against or not voting on the grounds it would clip the comandante's wings but not derail the policies favourable to the poor. He has another five years in office, regardless of the outcome.

Now that Chavez has said the vote is about him and rendered the details of the proposed changes secondary, many of these 'light chavistas' are expected to return to the fold. As a campaign tactic it cannot be faulted and could swing the vote his way. The official opposition is discredited, fragmented and no match for the state-backed Chavez juggernaut and cult of personality. Murals and media blitzes preaching solidarity with the comandante are ubiquitious.

With the President's supporters dominating parliament, the supreme court, the central bank, state enterprises, state media and most levels of government, the checks on his power - and whims - must come from within 'chavismo'.

The purge of supporters who deviated even slightly from the referendum campaign shows why so few speak out. Dissent is quashed. Only supporters with obsequious salutes make it on to Chavez's televised talkathons. Figures who had the authority to stand up to him, such as the former Vice-President, Vicente Rangel, have been replaced with yes-men.

If the boss goes off at a tangent about how the 19th-century liberator Simon Bolivar was supposedly murdered, an implausible conspiracy theory, ministers and aides applaud. A manned mission to Jupiter could be announced and they would not miss a beat.

If Chavez wins today it will show that most Venezuelans are still with him. The question, as he pockets his new powers, is what will happen should they one day turn against him.